Present day marine radars are very high-powered systems that transmit many kilowatts of peak power and have great difficulty in dealing with exceptionally short ranges of a few feet within the confines of river channels and locks, in addition to providing fine range resolution at ranges of many nautical miles.
Navico provides a frequency modulated/continuous wave (FM/CW) radar for commercial marine radar applications. The actual waveform used by Navico is a single sawtooth having a 10% or higher duty cycle. Their system also uses separate transmit and receive antennas to provide isolation. The Navico system is expensive because it uses two antennas with transmitter electronics on the back of the transmit antenna and receiver electronics on the back of the receive antenna. Navico fails to generate an ultra-linear Frequency Modulation with exceptionally low phase noise. Navico fails to recognize that a sawtooth waveform will cause several problems for the signal processing system. Navico also fails to recognize that the antenna VSWR must be better than 1.2:1 across the operating frequency band and that there is a critical need to provide a means to cancel the phase noise of the transmitter in the receiver mixer by carefully designed circuit timing delay.